Handheld pipettes are utilized to aspirate one or more fluids from a first receptacle containing such fluids, generally a precise quantity of such fluid, and to dispense the fluid to a second receptacle where the fluid may be analyzed or otherwise tested. To prevent interaction between successive samples, while minimizing cleaning/sterilization requirements, disposable tips are typically mounted to the pipette nozzles. Since an operator using such a pipette may do hundreds of aspirations/dispensings in a single day, repetitive stress injuries are a common problem for such operators. Many complain of wrist and shoulder injuries caused by extended periods of pipetting using traditional axial pipette designs and forearm strain is also a common complaint.
One reason for these injuries is that the operator needs to tightly grip the generally cylindrical pipette, particularly when mounting or removing a tip therefrom, but also while performing aspirating and dispensing operations, the gripping force required being somewhat less, but still significant, during performance of the latter operations. Another potential source of injury is the fact that, for most operations, the user's wrist/hand must be rotated while performing the operation rather than being held in its natural or neutral position which is generally approximately 45° to both the horizontal and vertical. It is preferable that as much of the pipetting operation as possible be performed with the wrist/hand in the neutral position. Similarly, to avoid such stress injuries, it is desirable that the elbow and shoulder joints also be in their neutral posture or position at approximately the mid-point of their travel path. Stress is generally minimized for a given operation when the operation is performed with each joint in this position.
Another problem with existing designs is that, with the tip being an extension of the cylindrical pipette, the pipette is relatively long, making it difficult to maneuver and use under a laboratory fume hood and forcing the operator to hold the pipette above the receptacle being aspirated from or dispensed into. This places stress on the muscles and joints of the shoulder, which, over time, results in fatigue and can ultimately lead to injury. The position of the nozzle and tip away from the operator's fingers also reduces the operator's “feel” of the tip and make it more difficult for the operator to control the tip, adding further to the fatigue and strain of performing pipetting operations.
Another ergonomic problem for pipettes is that operator discomfort and injury can result from points on a pipette which cause high contact pressure on the operator's fingers, thumb or other portions of the operator's hand. This can result from buttons or keys on the pipette having local pressure points or from such points on the body of the pipette which is gripped by the operator. To avoid discomfort or injury, there should be no point on the pipette where more than 14 psi pressure is exerted on the operator's hand. Few, if any, existing pipettes satisfy this criteria.
It is also desirable, particularly when aspirating fluid, to be able to see the tip of the pipette during the operation so that the tip is immersed only to the extent necessary to aspirate the fluid. Deeper immersion can result in inaccurate aspiration of the fluid and can cause other potential problems.
A need therefore exists for an improved, more ergonomic, pipette design which requires less gripping force, and preferably little if any gripping force by the operator on the pipette both during the mounting and ejection of tips from the pipette nozzle and during the aspiration and dispensing of fluids using the pipette. Such design should also facilitate the user's joints, including elbow, shoulder and wrist/hand being held in their neutral or natural position during pipetting operations, facilitate easier access to laboratory fume hoods, position the pipette nozzle and tip close to the operator's fingers, and in particular, to the operator's forefinger, to provide optimum control of the tip and position the nozzle and tip so the tip can be viewed by the operator at least when aspirating fluid and so the operator's elbow or other part of the operator's arm may rest on the surface containing the receptacle on which the pipetting operation is being performed, thereby reducing strain on the operator's shoulder, and minimize contact pressure on all parts of the operator's hand. Since substantial differences exist in the size, and to a lesser extent shape, of operator hands and arms, it would also be desirable if various aspects of the pipette could be customized, for example by use of adjustable or replaceable components, and/or by use of adapters, so as to be able to optimize the ergonomics of the pipette for a given user. Finally, it is sometimes desirable to lay a pipette down in the middle of a pipetting operation to, for example, open the lid of the fluid source, move test tubes, push a button on a machine, adjust the opening of a fume hood to permit access thereto, to otherwise provide access to the fluid source or sink, etc. It should be possible to accomplish this function without leakage of fluid either into or from the pipette and without contamination of the tip. It should also be possible to quickly and easily grasp the pipette in proper position for usage, preferably by use of only one hand. These later objectives can in at least some cases best be achieved if the pipette can be in a “stand-up” position when not in use. While some existing pipettes provide a limited number of these capabilities, a pipette design providing all, or at least most, of these capabilities does not currently exist.